Valladolid, Spain, 15 July 2026
Indoor air quality has become an increasingly important issue for human health and well-being. While discussions on air pollution have traditionally focused on traffic, industry and urban emissions, people spend most of their time indoors. Over the past four years, the European project K-HEALTHinAIR has investigated how indoor air quality behaves in everyday environments and explored the tools that can help assess and improve it.
The research has been carried out in hospitals, homes, schools, student residences, university canteens, public markets and metro stations across several European countries. The project combined continuous environmental monitoring with targeted sampling techniques, data analysis and health-related studies.
Now entering its final phase, the project has generated a more comprehensive understanding of the factors that influence indoor air quality in different environments. Indoor pollutants may originate from building materials, furniture, cleaning products, HVAC systems or everyday human activities. Their interpretation also requires consideration of environmental variables, whose influence varies depending on the characteristics and use of each space. The project's findings demonstrate that simply installing sensors and collecting measurements is not enough. Effective indoor air quality management requires selecting the right indicators, interpreting data in relation to occupancy, ventilation, activities and outdoor conditions, and translating this information into preventive actions through intuitive and accessible decision-support tools suitable for different user groups.
Real-life scenarios to understand a complex challenge
K-HEALTHinAIR combines continuous monitoring through sensors with targeted sampling and analytical campaigns to investigate indoor pollutants, identify their potential sources and determinants, and assess their relationship with human health.
The project has been implemented across real-life settings in several European countries. In Barcelona, research was conducted in different areas of Hospital Clínic, a metro station and a municipal market, alongside dedicated monitoring of patients with respiratory diseases in their homes. In Rotterdam, activities focused on older adults and outpatients. In Norway, the project investigated student residences, university canteens and classrooms, while in Poland and Austria research was carried out in schools and residential buildings.
This diversity of settings has enabled comparisons between environments with very different characteristics and requirements. Hospitals require stricter environmental control because of the vulnerability of patients, while prolonged occupancy is often the main challenge in classrooms. In canteens, markets and homes, cooking and cleaning activities can generate short-term emissions, whereas metro stations are strongly influenced by outdoor airflows and passenger movements.
The results demonstrate that there is no universal solution for indoor air quality management. Carbon dioxide is a valuable indicator of ventilation performance relative to occupancy, but it must be interpreted together with other pollutants such as particulate matter, volatile organic compounds (VOCs) and formaldehyde, as well as environmental variables including temperature, humidity and outdoor conditions.
Turning data into decisions
One of K-HEALTHinAIR's main achievements has been the development of tools capable of integrating, visualising and interpreting the information collected across the different pilot sites. Their purpose is to transform large volumes of environmental data into clear and actionable information for building managers, healthcare facilities, educational institutions, public authorities and other users.
Continuous monitoring makes it possible to identify patterns that would otherwise remain unnoticed, including pollutant peaks associated with specific activities, periods of insufficient ventilation, infiltration of outdoor pollution and differences between areas within the same building. This information can support decisions such as adjusting ventilation according to actual occupancy, improving HVAC maintenance, controlling specific emission sources and scheduling targeted interventions at the most appropriate times.
The practical value of this approach has already been demonstrated in one of the pilot sites. Hospital Clínic Barcelona has expanded its sensor network using its own funding, building on the work initiated within the project. In healthcare settings, continuous environmental monitoring can help evaluate ventilation performance, detect abnormal situations and support preventive decision-making across areas with different functional requirements.
Beyond healthcare environments, the results emphasise the importance of tailoring solutions to each specific context. In homes, everyday activities such as cooking, cleaning, smoking and ventilation have a significant influence on indoor air quality. In schools, university classrooms and student residences, occupancy and air renewal are particularly important factors, while in markets and metro stations indoor air quality is strongly affected by operating schedules, passenger flows, ventilation systems and outdoor environmental conditions.
An international conference hosted in Valladolid
The project's results were presented on 22–23 June at the Royal Academy of Medicine and Surgery of Valladolid during the international conference Healthy Indoors: Innovation and Research in Air Quality. The event brought together researchers, healthcare professionals, policymakers and other stakeholders to discuss environmental monitoring, indoor pollutants, health impacts, artificial intelligence and public policies for indoor air quality.
The conference also featured strong local participation. Researchers from the University of Valladolid and Río Hortega University Hospital presented studies on indoor environmental quality, while students from Condesa Eylo Alfonso and Emilio Ferrari secondary schools showcased their own classroom air quality research.
Towards preventive building management
Monitoring technologies offer new opportunities for managing indoor environments but cannot replace the need to address pollution at its source. Reducing or eliminating emission sources, selecting low-emission materials and products, properly maintaining HVAC systems and implementing ventilation strategies tailored to each situation remain fundamental measures.
These actions must also be complemented by improvements in outdoor air quality, which can significantly influence indoor pollutant concentrations and should therefore be considered when defining ventilation strategies.
Research led by CARTIF has demonstrated that understanding exactly what people breathe in hospitals, schools, homes, markets, transport systems and canteens is an essential step towards reducing health risks and improving well-being. At a time when health, energy efficiency and digital technologies are becoming increasingly integrated within the built environment, monitoring indoor air quality is evolving from an experimental practice into a practical tool for supporting better-informed decisions.
More information about the K-HEALTHinAIR project, together with materials and resources developed as part of the project, is available at: www.k-healthinair.eu.